| Mitchell & SON Groundworks Ltd | Construction | 2025 |
| Mitchell Holdings (SW) Limited | Other services | 2020 |
| Mitchell Home Services Ltd | Construction | 2025 |
| Mitchell Property Developments Limited | Real estate | 2016 |
| Mitchell Property Investments (SW) Ltd | Real estate | 2017 |
| MJ Electrical (SW) Ltd | Construction | 2025 |
| MJE Electrical Ltd | Construction | 2023 |
| MJM Structures Ltd | Other services | 2019 |
| MJR Construction (SW) Limited | Construction | 2003 |
| MK Elite Cleans Ltd | Administrative & support | 2026 |
| Mkst Properties Limited | Real estate | 2024 |
| Moat Units Ltd | Real estate | 2020 |
| Moby Nicks Limited | Wholesale & retail | 2000 |
| Modbury Chef Limited | Hospitality | 2024 |
| Modbury Messenger CIC | Information & communication | 2018 |
| Modular Tech Support Ltd | Information & communication | 2025 |
| Monarch Liqueurs Limited | Manufacturing | 2009 |
| Mondopeople LLP | | 2001 |
| Monofloor Technology Limited | Professional & scientific | 1994 |
| Montana Bar Plymouth Ltd | Hospitality | 2026 |
| Moor Sands Limited | Wholesale & retail | 2023 |
| MOOR2SEA Fencing Limited | Agriculture & fishing | 2024 |
| Moorclose Parking Ltd | Other services | 2008 |
| Moorhaven Agricultural Limited | Construction | 2020 |
| Moorhaven Holdings Limited | Financial services | 2019 |
| Moorhaven Ltd | Construction | 2004 |
| Moorhaven Rural Limited | Construction | 2019 |
| Moorhaven Village Management Company Limited | Administrative & support | 1994 |
| Moorland Mutts Ivybridge Ltd | Other services | 2026 |
| More Than Most Ltd | Wholesale & retail | 2004 |
| Morley Property Limited | Real estate | 2020 |
| Motortronics UK Limited | Manufacturing | 1981 |
| Mowerman (SW) Ltd | Other services | 2024 |
| MP Dirty Works Ltd | Construction | 2026 |
| MPR (SW) Ltd | Manufacturing | 2024 |
| MR Builder Co SW Ltd | Construction | 2011 |
| MR Home Improvements (SW) Ltd | Construction | 2022 |
| MS Waste Disposal Ltd | Water & waste | 2024 |
| Ms-Cdmandsafetyservices Ltd | Professional & scientific | 2023 |
| Munera Limited | Construction | 2021 |
| Mutiny Marine Ltd | Manufacturing | 2024 |
| My Holiday Cornwall Ltd | Hospitality | 2008 |
| Myami Hair Salon Limited | Other services | 2026 |
| Mylemon Limited | Information & communication | 2009 |
| N D L Electrical Services Limited | Real estate | 2004 |
| N&T Bookkeeping and Payroll Ltd | Professional & scientific | 2025 |
| Naed Repip (Holdings) Limited | Financial services | 2017 |
| Naed Repip Ytreporp Limited | Real estate | 2021 |
| Najma Digital Ventures Ltd | Wholesale & retail | 2025 |
| Nandon Restaurant Ltd | Hospitality | 2017 |
| Napfis Limited | Administrative & support | 2006 |
| Nationwide Festivals Ltd | Arts & recreation | 2025 |
| NBM Properties Limited | Real estate | 2013 |
| NDF Civils and Property Services Limited | Construction | 2019 |
| Neale's Cavern Limited | Manufacturing | 2023 |
| Neuff Athletic Equipment Limited | Wholesale & retail | 2007 |
| New Beginning Productions Ltd | Arts & recreation | 2023 |
| New Eyes Consultancy Limited | Professional & scientific | 2015 |
| New Leaf Co-Creation Ltd | Professional & scientific | 2026 |
| New Wave Property Management Ltd | Administrative & support | 2017 |
| Newbuild South West Limited | Construction | 2023 |
| Newman Electrical Services Ltd | Construction | 2011 |
| Newmarket Leeds Ltd | Hospitality | 2023 |
| Nichjolls LLP | | 2024 |
| Nick Moore Electrical Services Limited | Construction | 2025 |
| Nick Smith Boatbuilders Ltd | Manufacturing | 2026 |
| Nighthawk Locum Services Limited | Professional & scientific | 2012 |
| Nikita Salon Limited | Other services | 2023 |
| NJF & SON Building Contractors Ltd | Construction | 2024 |
| Norfolk Canoes Limited | Wholesale & retail | 2009 |
| North Street Cheese Company Ltd | Wholesale & retail | 2021 |
| NS Metalcrafting Limited | Manufacturing | 2023 |
| Number Nine Limited | Households | 1984 |
| O'Brien Contracting Ltd | Construction | 2025 |
| O'Brien Properties South West Ltd | Real estate | 2025 |
| O'Connor Drywall Ltd | Construction | 2018 |
| Oakenham Ltd | Construction | 2021 |
| Oaklane South West Limited | Construction | 2020 |
| Obrien Anaesthesia Ltd | Health & social care | 2023 |
| Ocean City Decorators Ltd | Construction | 2025 |
| Ocean City Spaces Ltd | Hospitality | 2026 |
| Ocean City Transport Ltd | Transport & logistics | 2021 |
| Ocean Views 1 Ltd | Hospitality | 2024 |
| Oggy Oggy Barbican Limited | Hospitality | 2020 |
| Oggy Oggy Cornwall Street Limited | Hospitality | 2021 |
| Oggy Oggy Ivybridge Limited | Hospitality | 2020 |
| Oggy Oggy Pasties Plympton Ltd | Hospitality | 2019 |
| Oggy Oggy Plymstock Ltd | Hospitality | 2020 |
| Oggy Oggy Properties Ltd | Real estate | 2025 |
| Omira UDI Ltd | Arts & recreation | 2025 |
| One KAI Limited | Professional & scientific | 2023 |
| One of One Distilling Co. Ltd | Manufacturing | 2025 |
| One SET of Footprints CIC | Education | 2025 |
| Oner Investments Limited | Real estate | 2024 |
| Onthebone Limited | Hospitality | 2024 |
| OPA21 Ltd | Hospitality | 2025 |
| Optima Graphics Topsham Limited | Manufacturing | 2010 |
| Optimum Carpentry & Joinery Ltd | Construction | 2018 |
| Optimum Carpentry Holdings Ltd | Financial services | 2026 |
| Optimum Fire Doors Ltd | Manufacturing | 2026 |